Major nations have failed to agree to set a goal halving greenhouse gas emissions by 2050, according to a draft document ahead of talks tomorrow - a setback to efforts to secure a new UN climate pact.

Neogotiations involving senior officials from the 17-nation Major Economies Forum broke down overnight after China and India opposed any mention of the target, a source familiar with negotiations told Reuters.

They first want to see rich nations commit to making deep cuts in their own emissions by 2020 and they want developed nations to work out plans to provide developing nations with short-term finance to help them cope with ever more floods, heatwaves, storms and rising sea levels, the source said.

The officials had been trying to lay the ground for an MEF summit tomorrow that will be chaired by U.S. President Barack Obama and Silvio Berlusconi of Italy, which chairs the G8.

The removal of a reference in the MEF draft to halving emissions by 2050 is a blow to efforts to secure a new U.N. climate pact in December.

Last year the G8 outlined a "vision" of halving emissions by 2050, without setting a base year. Major developing countries did not sign up for a 2050 goal, arguing the rich first had to set deep cuts in their own national emissions by 2020.

A draft G8 statement seen by Reuters today agreed the rise on global temperatures should not exceed 2 degrees Celsius. That would mark a breakthrough by EU states in convincing the United States, Japan, Russia and Canada that a 2 degrees Celsius (3.6 degrees Fahrenheit) limit is the necessary threshold beyond which climate change will reach danger levels.